Duncan faces the death penalty on three of 10 federal charges related to the 2005 kidnapping of young Dylan and Shasta Groene, of Coeur d'Alene, and the slaying of Dylan. A hearing on whether Duncan should be allowed to represent himself during the sentencing hearing will be held Monday.

Earlier this year, Duncan had asked U.S. District Judge Edward Lodge to allow him to represent himself, saying his attorneys could not "ethically represent my ideologies."

Duncan is able to rationally consult with his lawyer and has a factual understanding of the proceedings against him, Lodge wrote, describing Duncan as "articulate, intelligent and knowledgeable of these proceedings."

"Though he may have expressed unusual views or ideas, Mr. Duncan has not displayed any irrational behavior to the court," Lodge wrote. "Mr. Duncan has been polite, followed courtroom etiquette, and has appeared to be actively involved with his counsel."

An evaluator with the Bureau of Prisons found no evidence of any mental disorders or defects, nor a history of psychosis and mood or thought disorders, Lodge said.

An evaluator selected by the defense team, whose name was redacted from the ruling, found Duncan wasn't rationally able to understand the proceedings or assist in his defense, but Lodge said he found that opinion to be less credible than the bureau's official.

Duncan, a convicted pedophile from Tacoma, Wash., pleaded guilty in December to the federal charges related to the kidnapping of Shasta, then 8, and her brother Dylan, 9. The children were taken from their Coeur d'Alene home in May 2005 after Duncan fatally bludgeoned the children's mother, Brenda Groene, their 13-year-old brother Slade, and the mother's fiance, Mark McKenzie.

Both children were sexually abused before Duncan shot and killed Dylan at a campsite in western Montana. Shasta was rescued on July 2, 2005, when a waitress spotted Duncan and the girl in a Coeur d'Alene restaurant.

It will be up to Duncan's penalty phase jurors to decide whether he gets the death penalty or life in prison without parole.

Duncan earlier pleaded guilty in state court to murdering McKenzie and Slade and Brenda Groene before driving away with the two children. Sentencing on those state counts is not at issue here.